CA1092966A - Method of oil recovery employing enriched gas drive with control of evolved gas - Google Patents
Method of oil recovery employing enriched gas drive with control of evolved gasInfo
- Publication number
- CA1092966A CA1092966A CA294,318A CA294318A CA1092966A CA 1092966 A CA1092966 A CA 1092966A CA 294318 A CA294318 A CA 294318A CA 1092966 A CA1092966 A CA 1092966A
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- CA
- Canada
- Prior art keywords
- reservoir
- gas
- well means
- solvent
- produced
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000011084 recovery Methods 0.000 title claims abstract description 12
- 239000002904 solvent Substances 0.000 claims abstract description 52
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 39
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 36
- 238000004519 manufacturing process Methods 0.000 claims abstract description 32
- 238000002347 injection Methods 0.000 claims abstract description 22
- 239000007924 injection Substances 0.000 claims abstract description 22
- 230000007704 transition Effects 0.000 claims abstract description 20
- 239000004215 Carbon black (E152) Substances 0.000 claims abstract description 15
- 239000012530 fluid Substances 0.000 claims abstract description 15
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 13
- 239000007789 gas Substances 0.000 claims description 69
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 28
- 239000000203 mixture Substances 0.000 claims description 16
- 238000007598 dipping method Methods 0.000 claims description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 4
- 125000004432 carbon atom Chemical group C* 0.000 claims description 4
- 239000003915 liquefied petroleum gas Substances 0.000 claims description 4
- 239000003345 natural gas Substances 0.000 claims description 4
- 239000012267 brine Substances 0.000 claims description 3
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 2
- 239000001569 carbon dioxide Substances 0.000 claims description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 2
- 239000003546 flue gas Substances 0.000 claims description 2
- 230000006872 improvement Effects 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 125000001183 hydrocarbyl group Chemical group 0.000 abstract 1
- 230000008569 process Effects 0.000 description 13
- 239000000543 intermediate Substances 0.000 description 11
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 239000001294 propane Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 239000003570 air Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229920002401 polyacrylamide Polymers 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- -1 that is Chemical class 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/18—Repressuring or vacuum methods
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/166—Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium
- E21B43/168—Injecting a gaseous medium
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Gas Separation By Absorption (AREA)
Abstract
METHOD OF OIL RECOVERY EMPLOYING
ENRICHED GAS DRIVE WITH CONTROL OF
EVOLVED GAS
(D#73,702-F) ABSTRACT OF THE DISCLOSURE
A method for the recovery of hydrocarbons from a subterranean hydrocarbon-bearing reservoir by an enriched gas drive wherein lean gas, evolved from the miscible transition zone, is produced ahead of the miscible transition zone and reinjected behind the solvent injection point whereby excessive gas production is utilized and a drive agent miscible with the solvent is provided to displace the reservoir fluids through the reservoir to a production well from which they are produced.
ENRICHED GAS DRIVE WITH CONTROL OF
EVOLVED GAS
(D#73,702-F) ABSTRACT OF THE DISCLOSURE
A method for the recovery of hydrocarbons from a subterranean hydrocarbon-bearing reservoir by an enriched gas drive wherein lean gas, evolved from the miscible transition zone, is produced ahead of the miscible transition zone and reinjected behind the solvent injection point whereby excessive gas production is utilized and a drive agent miscible with the solvent is provided to displace the reservoir fluids through the reservoir to a production well from which they are produced.
Description
10~2966 FIELD OF TH~ IN~ENTION
This invention relates to a method for the recovery of hydrocarbons from a subterranean reservoir utilizing an en-riched gas drive wherein lean gas evolved from the miscible transition zone is produced ahead of the solvent-oil transition zone and reinjected behind the point of solvent injection, thereby utilizing the produced lean gas as a drive agent to produce the reservoir and minimizing the amount of lean gas reaching the producing wells.
PRIOR ART
In the recovery of oil from subterranean reservoirs, one method that is utilized to enhance recovery is the use of a solvent for the oil to wash the oil out of the reservoir.
When the solvent employed can mix completely with the oil to form a single phase the term "miscible flooding" is applied ~`
to the process. -The effectiveness of the miscible recovery process is based on the fact that a two-phase system within the reser-voir between t~e solvent displacing agent and the oil is 2a eliminated at the reservoir conditions of temperature and pressure, thereby eliminating interfacial tension and hence the retentive capillary forces. When these retentive forces are pr~sent in flooding operations where the displacing agent and the reservoir oil are not miscible with each other, but exist as two phases in the reservoir, recovery efficiency is significantly reduced.
A misci~le flood process may employ either "first contact" miscibility or "conditional" miscibility. In the former type the injected solvent is miscible upon first ' ~
contact with the oil. Typically, first contact miscible processes utilize a solvent liquefiable at reservoir conditions with the solvent being rich in intermediate hydrocarbons, that is, hydrocarbons having from two to six carbon atoms in the molecule, such as propane or liquid petroleum gas (LPG~. Since it is not ganerally economical to use a barrel of solvent to produce a barrel of oil, the solvent is injected as a slug in an amount sufficient to establish a miscible transition zone at the "leading edge"
of the solvent slug between the solvent and the reservoir hyarocarbons. Thereafter~ a less costly drive agent is injected that may or may not be miscible with the solvent at the "trailing edge" of the solvent slug. For example, if the drive agent employed is natural gas or methane, "trailing edge" miscibility generally will exist at reservoir conditions.
In a "conditional miscible" flood, a gas drive is employed wherein the gas injected contains a reduced amount ,~
of a solvent. Where miscibility is established in the reservoir by the solvent in the gas being absorbed by the reservoir hydrocarbon or oil, thereby building up a miscible transition zone of an oil bank rich in solvent ahead of the drive gas, the process is also termed an "enriched gas drive".
The enriched gas ~rive generally utilizes a lean hydrocarbon gaseous solvent o~ a mixture of methane and intermediate hydrocarbons having from two to six carbon atoms in the molecule. Propane or LPG are the intermediates usually employed. The minimum amount of solvent necessary to establish
This invention relates to a method for the recovery of hydrocarbons from a subterranean reservoir utilizing an en-riched gas drive wherein lean gas evolved from the miscible transition zone is produced ahead of the solvent-oil transition zone and reinjected behind the point of solvent injection, thereby utilizing the produced lean gas as a drive agent to produce the reservoir and minimizing the amount of lean gas reaching the producing wells.
PRIOR ART
In the recovery of oil from subterranean reservoirs, one method that is utilized to enhance recovery is the use of a solvent for the oil to wash the oil out of the reservoir.
When the solvent employed can mix completely with the oil to form a single phase the term "miscible flooding" is applied ~`
to the process. -The effectiveness of the miscible recovery process is based on the fact that a two-phase system within the reser-voir between t~e solvent displacing agent and the oil is 2a eliminated at the reservoir conditions of temperature and pressure, thereby eliminating interfacial tension and hence the retentive capillary forces. When these retentive forces are pr~sent in flooding operations where the displacing agent and the reservoir oil are not miscible with each other, but exist as two phases in the reservoir, recovery efficiency is significantly reduced.
A misci~le flood process may employ either "first contact" miscibility or "conditional" miscibility. In the former type the injected solvent is miscible upon first ' ~
contact with the oil. Typically, first contact miscible processes utilize a solvent liquefiable at reservoir conditions with the solvent being rich in intermediate hydrocarbons, that is, hydrocarbons having from two to six carbon atoms in the molecule, such as propane or liquid petroleum gas (LPG~. Since it is not ganerally economical to use a barrel of solvent to produce a barrel of oil, the solvent is injected as a slug in an amount sufficient to establish a miscible transition zone at the "leading edge"
of the solvent slug between the solvent and the reservoir hyarocarbons. Thereafter~ a less costly drive agent is injected that may or may not be miscible with the solvent at the "trailing edge" of the solvent slug. For example, if the drive agent employed is natural gas or methane, "trailing edge" miscibility generally will exist at reservoir conditions.
In a "conditional miscible" flood, a gas drive is employed wherein the gas injected contains a reduced amount ,~
of a solvent. Where miscibility is established in the reservoir by the solvent in the gas being absorbed by the reservoir hydrocarbon or oil, thereby building up a miscible transition zone of an oil bank rich in solvent ahead of the drive gas, the process is also termed an "enriched gas drive".
The enriched gas ~rive generally utilizes a lean hydrocarbon gaseous solvent o~ a mixture of methane and intermediate hydrocarbons having from two to six carbon atoms in the molecule. Propane or LPG are the intermediates usually employed. The minimum amount of solvent necessary to establish
-2-.
, ~296 Ei miscibility in an enriched gas drive depends upon reservoir conditions of temperature and pressure and the physical and chemical characteristics o the hydrocarbons in the reservoir.
This amount can be determined by mleans of laboratory displace-ment tests or equilibrium studies of the PVT behavior of the hydrocarbon components which tests are well-known in the art.
For example a method for determining composition of an enriched gas that has conditional miscibility with the reser-voir hydrocarbons at the pressure and temperature of the 19 reservoir is set forth in U. S. Patent 3,854,532. In this patent there is taught that for a given set of conditions of temperature and pressure for a reservoir, there exists a mixture of hydrocarbons having a composition such that upon successive contacts with the reservoir hydrocarbons or oil the mixture will form with the reservoir hydrocarbon or oil, a single fluid phase by the absorption of the intermediate `
hydrocarbons of the mixture. This patent also describes the process in terms of a three-component composition diagram, of~en referred to as a ternary diagram which depicts the ~0 phase relations between the various components for given reservoir conditions of temperature and pressure.
One of the difficulties of the enriched gas drive process relates to the fact that the injected solvent is gaseous at reservoir conditions and miscibility occurs by the continued absorption of the intermediate hydrocarbons into the oil. Concurrent with this absorption the remaining gas primarily methane from the injected gas mixture being more mobile is displaced through the reservoir ahead of the solvent transition zone, to be later produced via production 29~i6 wells. As the process continues, more and more gas is displaced through the reservoir and as production continues, the produced fluids become very high in gas content as evidenced by increasing gas-oil ratios. Eventually, as the permeability of the reservoir to gas increases because of the increased gas saturation, very high produced gas-oil ratios are realized, and very little liquid hydrocarbon or oil is displaced and produced. Under these conditions undesirable gas override may also occur in the reservoir, with consequent little movement or production of the reservoir hydrocarbons. In the limit these undesirable conditions may necessitate shutting in the producing wells.
By our invention in an enriched gas drive the lean gas is produced ahead of the formed miscible transition zone and is reinjected behind the injection point for the solvent, thereby utilizing the gas evolved from the miscible transition zone and further providing a drive agent for the enriched gas drive.
SUMMARY OF THE INVENTION
This invention relates to a method of recovery of : hydrocarbons from a dipping reservoir traversed by a first injection well means completed in the upper horizon of the ;~
reservoir and a second production well means completed in the lower horizon of the reservoir wherein a solvent that is conditionally miscible with the reservoir oil is injected via the first in;ection well means and fluids are produced via the second production well means comprising the steps of:
a. providing a third well means intermediate between said first inJection well means and said second ~ ~ .
, ~9z9~
production well means for producing fluids from said reservoir, b. providing a fourth well means behind said first iniection well means for injecting fluids, c. producing fluids comprising principally gas from said third well means when the ratio of produced gas to produced oil from said second production well means has become undesirably high, d. compressing said produced gas to a pressure above the reservoir pressure of said reservoir, and injecting said gas into said reservoir via said fourth well means, thereby providing a drive agent to displace said reservoir fluids through said reservoir, toward said second production well means.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 depicts ~he application of an enriched gas drive process to a dipping reservoir.
Figure 2 depicts the advances in the art in accordance with this invention.
DESCRIPTION OF THE INVENTION
:` In its broadest aspect this invention relates to an improved enriched gas drive for the recovery of reservoir hydrocarbons wherein the lean gas evolved from a miscible transition zone is utilized as a drive agent. In one (a) .
~V~2966 embodiment of the invention the process is applied to a dipping reservoir. In this case t~e reservoir is penetrated by at least one crestal injection well or a well completed behind the solvent bank. The reservoir also is penetrated by at least one production well that :is completed into the lower portion of the hydrocarbon-saturated zone. Tn operation, a gaseous solvent, that is conditionally miscible with the reser-voir hydrocarbons, is injected via the injection well into the reservoir~ Upon contact with the reservoir hydrocarbons the intermediate hydrocarbons of the solvent such as propane are a~sorbed by the reservoir hydrocarbons, thereby forming a miscible transition zone between the injected solvent and the reservoir ~ydrocarbons. ~ith the absorption of the interme-diates the remaining portion of the hydrocarbon solvent becomes leaner and the gas, principally methane, and other relatively noncondensable gases, which are not absorbed and being more mobile are displaced through the reservoir, in the direction of the producing well. In the conventional operation, as set forth above, this may result in excessive gas production with little liquid hydrocarbon production.
By the invention, after the lean gas starts to accu-mulate in t~e reservoir ahead of the transition zone between the solvent and the reservoir hydrocarbons, and an increase in the gas-oil ratio becomes evident, a third well means is provided that penetrates the reservoir ahead of the formed transition zone. Its completion provides for production from only the upper horizon of the reservoir. Location of this third well means can be determined by known techniques as applied to reservoirs. Thereafter, this well means is produced, its production being principally gas. The produced yas being very lean in composition is compressed, without separation into its components, and reinjected via a fourth well means behind the point of injection of the solvent material. Thus, the injected gas serves as a drive agent to displace the injected solvent and the oil through the reservoir. In addition, a trailing edge misci~le zone is created within the reservoir t~at serves to improve recovery of the lighter hydrocarbons in t.~e reservoir, both present initially and also from the in~ected solvent. By the method of operation,gas breakthrough into t~e producing well is controlled so that improved dis-placement of the liquid hydrocarbons is attained because of the more favorable relative permeability conditions in the reservoir.
One embodiment of the invention may be illustrated by referring to the accompanying figures. Figure 1 depicts a schematic version of a conventional enriched gas arive as applied to a dipping raservoir (1). In this method, the enriched gas solvent, whose composition has been previously established, is injected via injection well (2) completed by ; conventional means in the updip portion of the oil column of the reservoir or to the gas/oil interface. A production well
, ~296 Ei miscibility in an enriched gas drive depends upon reservoir conditions of temperature and pressure and the physical and chemical characteristics o the hydrocarbons in the reservoir.
This amount can be determined by mleans of laboratory displace-ment tests or equilibrium studies of the PVT behavior of the hydrocarbon components which tests are well-known in the art.
For example a method for determining composition of an enriched gas that has conditional miscibility with the reser-voir hydrocarbons at the pressure and temperature of the 19 reservoir is set forth in U. S. Patent 3,854,532. In this patent there is taught that for a given set of conditions of temperature and pressure for a reservoir, there exists a mixture of hydrocarbons having a composition such that upon successive contacts with the reservoir hydrocarbons or oil the mixture will form with the reservoir hydrocarbon or oil, a single fluid phase by the absorption of the intermediate `
hydrocarbons of the mixture. This patent also describes the process in terms of a three-component composition diagram, of~en referred to as a ternary diagram which depicts the ~0 phase relations between the various components for given reservoir conditions of temperature and pressure.
One of the difficulties of the enriched gas drive process relates to the fact that the injected solvent is gaseous at reservoir conditions and miscibility occurs by the continued absorption of the intermediate hydrocarbons into the oil. Concurrent with this absorption the remaining gas primarily methane from the injected gas mixture being more mobile is displaced through the reservoir ahead of the solvent transition zone, to be later produced via production 29~i6 wells. As the process continues, more and more gas is displaced through the reservoir and as production continues, the produced fluids become very high in gas content as evidenced by increasing gas-oil ratios. Eventually, as the permeability of the reservoir to gas increases because of the increased gas saturation, very high produced gas-oil ratios are realized, and very little liquid hydrocarbon or oil is displaced and produced. Under these conditions undesirable gas override may also occur in the reservoir, with consequent little movement or production of the reservoir hydrocarbons. In the limit these undesirable conditions may necessitate shutting in the producing wells.
By our invention in an enriched gas drive the lean gas is produced ahead of the formed miscible transition zone and is reinjected behind the injection point for the solvent, thereby utilizing the gas evolved from the miscible transition zone and further providing a drive agent for the enriched gas drive.
SUMMARY OF THE INVENTION
This invention relates to a method of recovery of : hydrocarbons from a dipping reservoir traversed by a first injection well means completed in the upper horizon of the ;~
reservoir and a second production well means completed in the lower horizon of the reservoir wherein a solvent that is conditionally miscible with the reservoir oil is injected via the first in;ection well means and fluids are produced via the second production well means comprising the steps of:
a. providing a third well means intermediate between said first inJection well means and said second ~ ~ .
, ~9z9~
production well means for producing fluids from said reservoir, b. providing a fourth well means behind said first iniection well means for injecting fluids, c. producing fluids comprising principally gas from said third well means when the ratio of produced gas to produced oil from said second production well means has become undesirably high, d. compressing said produced gas to a pressure above the reservoir pressure of said reservoir, and injecting said gas into said reservoir via said fourth well means, thereby providing a drive agent to displace said reservoir fluids through said reservoir, toward said second production well means.
BRIEF DESCRIPTION OF THE FIGURES
Figure 1 depicts ~he application of an enriched gas drive process to a dipping reservoir.
Figure 2 depicts the advances in the art in accordance with this invention.
DESCRIPTION OF THE INVENTION
:` In its broadest aspect this invention relates to an improved enriched gas drive for the recovery of reservoir hydrocarbons wherein the lean gas evolved from a miscible transition zone is utilized as a drive agent. In one (a) .
~V~2966 embodiment of the invention the process is applied to a dipping reservoir. In this case t~e reservoir is penetrated by at least one crestal injection well or a well completed behind the solvent bank. The reservoir also is penetrated by at least one production well that :is completed into the lower portion of the hydrocarbon-saturated zone. Tn operation, a gaseous solvent, that is conditionally miscible with the reser-voir hydrocarbons, is injected via the injection well into the reservoir~ Upon contact with the reservoir hydrocarbons the intermediate hydrocarbons of the solvent such as propane are a~sorbed by the reservoir hydrocarbons, thereby forming a miscible transition zone between the injected solvent and the reservoir ~ydrocarbons. ~ith the absorption of the interme-diates the remaining portion of the hydrocarbon solvent becomes leaner and the gas, principally methane, and other relatively noncondensable gases, which are not absorbed and being more mobile are displaced through the reservoir, in the direction of the producing well. In the conventional operation, as set forth above, this may result in excessive gas production with little liquid hydrocarbon production.
By the invention, after the lean gas starts to accu-mulate in t~e reservoir ahead of the transition zone between the solvent and the reservoir hydrocarbons, and an increase in the gas-oil ratio becomes evident, a third well means is provided that penetrates the reservoir ahead of the formed transition zone. Its completion provides for production from only the upper horizon of the reservoir. Location of this third well means can be determined by known techniques as applied to reservoirs. Thereafter, this well means is produced, its production being principally gas. The produced yas being very lean in composition is compressed, without separation into its components, and reinjected via a fourth well means behind the point of injection of the solvent material. Thus, the injected gas serves as a drive agent to displace the injected solvent and the oil through the reservoir. In addition, a trailing edge misci~le zone is created within the reservoir t~at serves to improve recovery of the lighter hydrocarbons in t.~e reservoir, both present initially and also from the in~ected solvent. By the method of operation,gas breakthrough into t~e producing well is controlled so that improved dis-placement of the liquid hydrocarbons is attained because of the more favorable relative permeability conditions in the reservoir.
One embodiment of the invention may be illustrated by referring to the accompanying figures. Figure 1 depicts a schematic version of a conventional enriched gas arive as applied to a dipping raservoir (1). In this method, the enriched gas solvent, whose composition has been previously established, is injected via injection well (2) completed by ; conventional means in the updip portion of the oil column of the reservoir or to the gas/oil interface. A production well
(3) is completed downdip from which the displaced reservoir fluids are produced. An enriched gas solvent is injected via the injection well in amounts sufficient to form by condi-tional misci~ility a transition zone (4~ with the reservoir hydrocarbons. During the operation the gas, primarily methane, resulting from the solvent slug after having been stripped of its intermediates by their absorption in the oil, moves at the frontal portion of the transition zone (5).
Production of reservoir fluids from production well (3) occurs with increasing gas~oil ratio. With an excessive gas-oil ratio, production of reservoir liquid hydrocarbons diminishes to a point when further operation becomes uneconomical.
;~ Figure 2 depicts the improvement of the instant invention as applied to a dipping reservoir ~10), traversed by an injection well ~11) and a production well (12). Shown are two additional wells completed in the reservoir for the practice of the invention. Well ~13) is completed ahead of the formed transition zone (16) between the injected solvent and the reservoir hydrocarbons. The well is packed off such ` that production therefrom is restricted to the upper horizon of the reservoir if override or gravity segregation has occurred. Well (14) is completed behind th~ injection well and serves as an injection well for the produced and then reinjected gas. ~ith increased gas-oil ratio from the produc-tion well tl2), well tl3~ is produced in a manner such that : its production is principally gas which is thereafter compressed by compressor means tlS) and reinjected behind the solvent injection well tll) via well tl4). Thus, there is provided a drive agent for the process, which drive agent is the reinjected gas. By the method of operation there is no phase change be-tween the reinjected gas and the solvent and a second tra~sition zone tl7) is formed at the trailing edge of the solvent slug.
In this manner, the enriched gas miscible slug process is transformed into a slug driven process, utilizing the excess ., .
~09296S
amounts of produced lean gas. Alternately, the produced gas can be recombined with intermediate hydrocarbon solvent to continuP an enriched gas drive.
The gaseous solvent for the process may be any hydrocarbon comprising methane or natural gas and at least one intermediate hydrocarbon having from two to six carbon atoms in the molecule. Its composition may be determined according to laboratory procedures as described heretofore and set forth in U.S.P. 3,854,532. The solvent is injected in amounts sufficient to establish the desired miscible transition zone. Generally, for an enriched gas drive, the amount of pore volumes of solvent injected is in the range of 3~ to 50%. While the solvent is usually injected alone, in instances where improved mobility control is sought, water or brine, either thickened or unthickened, may be injected simul- -taneously or alternately with the solvent. The use of thickeners, such as polyacrylamides, to increase the viscosity of aqueous liquids thereby improving mobility control is well-Xnown in the art. `~
In summary, in accordance with the invention a reservoir is produced by an enriched gas drive until an -undesirably high gas-oil ratio occurs. Thereafter, additional production of the reservoir is undertaken from the reservoir by a well means 'Located ahead of the miscible transition front.
The location of the well means and method of completion are such that the principal production therefrom is the gas resulting from the mechanism of the enriched gas drive. This gas J~9;;~966 production is cycled and reinjected behind the original injection well whereby the injected gas provides a drive mechanism to displace the miscible zone and the oil through :
the reservoir. In some instances it may be necessary or desirable to supplement the reinjected gas with make-up gas such as methane, natural gas, carbon dioxide, nitrogen, air, or flue gas. Additionally, this produced gas may be combined ~`
with solvent and injected as enriched gas via the original injection well. .
~ .
_g_ : ~
Production of reservoir fluids from production well (3) occurs with increasing gas~oil ratio. With an excessive gas-oil ratio, production of reservoir liquid hydrocarbons diminishes to a point when further operation becomes uneconomical.
;~ Figure 2 depicts the improvement of the instant invention as applied to a dipping reservoir ~10), traversed by an injection well ~11) and a production well (12). Shown are two additional wells completed in the reservoir for the practice of the invention. Well ~13) is completed ahead of the formed transition zone (16) between the injected solvent and the reservoir hydrocarbons. The well is packed off such ` that production therefrom is restricted to the upper horizon of the reservoir if override or gravity segregation has occurred. Well (14) is completed behind th~ injection well and serves as an injection well for the produced and then reinjected gas. ~ith increased gas-oil ratio from the produc-tion well tl2), well tl3~ is produced in a manner such that : its production is principally gas which is thereafter compressed by compressor means tlS) and reinjected behind the solvent injection well tll) via well tl4). Thus, there is provided a drive agent for the process, which drive agent is the reinjected gas. By the method of operation there is no phase change be-tween the reinjected gas and the solvent and a second tra~sition zone tl7) is formed at the trailing edge of the solvent slug.
In this manner, the enriched gas miscible slug process is transformed into a slug driven process, utilizing the excess ., .
~09296S
amounts of produced lean gas. Alternately, the produced gas can be recombined with intermediate hydrocarbon solvent to continuP an enriched gas drive.
The gaseous solvent for the process may be any hydrocarbon comprising methane or natural gas and at least one intermediate hydrocarbon having from two to six carbon atoms in the molecule. Its composition may be determined according to laboratory procedures as described heretofore and set forth in U.S.P. 3,854,532. The solvent is injected in amounts sufficient to establish the desired miscible transition zone. Generally, for an enriched gas drive, the amount of pore volumes of solvent injected is in the range of 3~ to 50%. While the solvent is usually injected alone, in instances where improved mobility control is sought, water or brine, either thickened or unthickened, may be injected simul- -taneously or alternately with the solvent. The use of thickeners, such as polyacrylamides, to increase the viscosity of aqueous liquids thereby improving mobility control is well-Xnown in the art. `~
In summary, in accordance with the invention a reservoir is produced by an enriched gas drive until an -undesirably high gas-oil ratio occurs. Thereafter, additional production of the reservoir is undertaken from the reservoir by a well means 'Located ahead of the miscible transition front.
The location of the well means and method of completion are such that the principal production therefrom is the gas resulting from the mechanism of the enriched gas drive. This gas J~9;;~966 production is cycled and reinjected behind the original injection well whereby the injected gas provides a drive mechanism to displace the miscible zone and the oil through :
the reservoir. In some instances it may be necessary or desirable to supplement the reinjected gas with make-up gas such as methane, natural gas, carbon dioxide, nitrogen, air, or flue gas. Additionally, this produced gas may be combined ~`
with solvent and injected as enriched gas via the original injection well. .
~ .
_g_ : ~
Claims (9)
1. A method of oil recovery from a subterranean hydrocarbon-bearing dipping reservoir, traversed by a first injection well means completed in the upper horizon of such reservoir and a second production well means completed in the lower horizon of said reservoir wherein a solvent that is gaseous at the reservoir conditions of temperature and pressure and conditionally miscible with the reservoir hydrocarbon is injected via first injection well means into said reservoir to form a miscible transition zone with said reservoir hydrocarbon, and reservoir fluids are produced via said second production well means, the improvement comprising:
a. providing a third well means intermediate between said first injection well means and said second production well means for producing fluids from said reservoir, b. providing a fourth well means behind said first injection well means for injecting fluids, c. producing fluids comprising principally gas from said third well means when the ratio of produced gas to produced oil from said second production well means has become undesirably high, d. compressing said produced gas to a pressure above the reservoir pressure of said reservoir, and injecting said gas into said reservoir via said fourth well means, thereby providing a drive agent to displace said reservoir fluids through said reservoir, toward said second production well means.
a. providing a third well means intermediate between said first injection well means and said second production well means for producing fluids from said reservoir, b. providing a fourth well means behind said first injection well means for injecting fluids, c. producing fluids comprising principally gas from said third well means when the ratio of produced gas to produced oil from said second production well means has become undesirably high, d. compressing said produced gas to a pressure above the reservoir pressure of said reservoir, and injecting said gas into said reservoir via said fourth well means, thereby providing a drive agent to displace said reservoir fluids through said reservoir, toward said second production well means.
2. The method of Claim 1 wherein said third well means is completed into the upper portion of said reservoir.
3. The method of Claim 1 wherein said third well means is located between said injection well means and said production well means in spaced relation to said miscible transition zone.
4. The method of Claim 1 wherein said fourth well means comprises a well completed across the horizon of said reservoir.
5. The method of Claim 1 wherein said solvent comprises a mixture of methane and at least one hydrocarbon having from two to six carbon atoms per molecule.
6. The method of Claim 5 wherein said mixture comprises methane and liquid petroleum gas.
7. The method of Claim l wherein water, brine, thickened water, thickened brine and mixtures thereof are injected simultaneously or alternately with said solvent.
8. The method of Claim 1 wherein methane, natural gas, carbon dioxide, nitrogen, flue gas and mixtures thereof is added to said produced gas prior to injection into said reservoir.
9. The method of Claim 1 wherein said produced gas is combined with solvent and reinjected as the gaseous solvent for a continued enriched gas drive.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/758,268 US4086961A (en) | 1977-01-10 | 1977-01-10 | Method of oil recovery employing enriched gas drive with control of evolved gas |
| US758,268 | 1977-01-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1092966A true CA1092966A (en) | 1981-01-06 |
Family
ID=25051143
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA294,318A Expired CA1092966A (en) | 1977-01-10 | 1978-01-04 | Method of oil recovery employing enriched gas drive with control of evolved gas |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4086961A (en) |
| CA (1) | CA1092966A (en) |
| MX (1) | MX5041E (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4299286A (en) * | 1980-05-21 | 1981-11-10 | Texaco Inc. | Enhanced oil recovery employing blend of carbon dioxide, inert gas _and intermediate hydrocarbons |
| US4427067A (en) | 1982-08-06 | 1984-01-24 | Exxon Production Research Co. | Water and miscible fluid flooding method having good vertical conformance for recovering oil |
| US4794987A (en) * | 1988-01-04 | 1989-01-03 | Texaco Inc. | Solvent flooding with a horizontal injection well and drive fluid in gas flooded reservoirs |
| CA2185837C (en) * | 1996-09-18 | 2001-08-07 | Alberta Oil Sands Technology And Research Authority | Solvent-assisted method for mobilizing viscous heavy oil |
| RU2511151C2 (en) * | 2012-07-26 | 2014-04-10 | Открытое акционерное общество "Российская инновационная топливно-энергетическая компания (ОАО "РИТЭК") | Method for recovery of residual oil reserves |
| CN104594943A (en) * | 2015-01-20 | 2015-05-06 | 大同煤矿集团有限责任公司 | Ground composite L-shaped drilling well for gas control and gas control method |
| RU2607133C1 (en) * | 2016-02-29 | 2017-01-10 | Публичное акционерное общество "Татнефть" им. В.Д. Шашина | Method for development of non-homogeneous oil deposit |
| CN111720116B (en) * | 2020-05-14 | 2021-09-14 | 中国石油化工股份有限公司 | Fracture-cavity type oil reservoir unit nitrogen gas flooding gas channeling judgment method and injection-production channeling prevention method |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3256933A (en) * | 1950-07-13 | 1966-06-21 | Exxon Production Research Co | Methods of recovery of oil |
| US3354953A (en) * | 1952-06-14 | 1967-11-28 | Pan American Petroleum Corp | Recovery of oil from reservoirs |
| US2994373A (en) * | 1957-12-18 | 1961-08-01 | Jersey Prod Res Co | Method of increasing oil recovery |
| US3157230A (en) * | 1960-12-16 | 1964-11-17 | Socony Mobil Oil Co Inc | Method of recovering oil from an oil-bearing reservoir |
| US3254712A (en) * | 1962-03-29 | 1966-06-07 | Socony Mobil Oil Co Inc | Miscible phase displacement method of recovering oil |
| US3223157A (en) * | 1963-04-09 | 1965-12-14 | Exxon Production Research Co | Oil recovery process |
| US3268000A (en) * | 1963-08-14 | 1966-08-23 | Shell Oil Co | Crude oil recovery by enriched gas drive |
| US3288212A (en) * | 1964-05-21 | 1966-11-29 | Union Oil Co | Secondary oil recovery method |
| US3854532A (en) * | 1972-10-06 | 1974-12-17 | Texaco Inc | Enriched gas drive recovery process |
-
1977
- 1977-01-10 US US05/758,268 patent/US4086961A/en not_active Expired - Lifetime
- 1977-09-27 MX MX776436U patent/MX5041E/en unknown
-
1978
- 1978-01-04 CA CA294,318A patent/CA1092966A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4086961A (en) | 1978-05-02 |
| MX5041E (en) | 1983-02-25 |
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